galaxy note 2 speakerphone switches off during calls

My phone lately keep switching off the speakerphone during calls, usually after a minute from placing the call. The software version of my phone is 4.1.2.
It's really annoying because you while you're talking on the phone thinking that the other party hearing you to find out that the speakerphone switched off by itself to the ears device.
any help please.

My phone lately keep switching off the speakerphone during calls, usually after a minute from placing the call. The software version of my phone is 4.1.2.
It's really annoying because you while you're talking on the phone thinking that the other party hearing you to find out that the speakerphone switched off by itself to the ears device.
any help please.